Geometry and origin of supergiant gold deposits in the Jiaodong gold province, eastern China

Abstract

Based on the new deep exploration results, the gold reserves of Jiaojia gold deposit and Sanshandao gold deposit of the Jiaodong gold province, eastern North China Craton (NCC), exceed 1300 and 1200 tons, respectively. Both deposits are distributed along adjacent faults of Jiaojia and Sanshandao, respectively, forming a globally significant supergiant deposit. The main orebodies are preserved along two low-angle steps on the faults, with Jiaojia orebodies deposited in left-stepping bends, and Sanshandao orebodies deposited in right-stepping bends. The above geometric distribution of orebodies of these two deposits is clearly related to the kinematics of the ore-controlling faults. Weideshan suite is the largest Cretaceous magmatic rocks in the Jiaodong peninsula, which is considered as a profound impact on the gold mineralization in Jiaodong. LA-ICP-MS U-Pb dating of magmatic zircons from the associated Weideshan suite granitoid yields ages of 121.3 ± 2.1 Ma and 116.7 ± 1.7 Ma, which are consistent with mineralization age of the gold deposits (ca. 120 Ma). On the basis of regional geological data, our study indicates that the large-scale magmatic activities in the Early Cretaceous of Weideshan suite provide thermodynamic conditions for gold mineralization. A metallogentic model suggests that the formation of Jiaodong type gold deposits may have involved a thermal doming-extension process during the Mesozoic decratonization of NCC. In the Early Cretaceous, mantle upwelling and crust-mantle interaction triggered magmatism and fluid activities. These activities were simultaneous with granitoid doming, crustal extension and detachment faulting, upgrading Au of gold deposits. Mantle-derived gold-bearing fluid mixed with crust-derived gold-bearing fluid precipitated from remelting lower crust, forming gold-rich fluid reservoir and producing gold-poor Weideshan suite granitoid. Subsequently, granitoid doming, crustal extension and detachment faulting occurred. This process provides both favorable channels for ore-forming fluid migration and potential locations for enriching and trapping fluids, forming supergiant ore deposits.